Showing papers on "Laser published in 1976"
TL;DR: The theoretical basis and some practical guidelines for simple, rigorous analysis of FPR experiments are presented and some model experiments on aqueous solutions of rhodamine 6G are described.
2,594 citations
Book•
01 Jan 1976TL;DR: In this paper, the Doppler Reference Record (DRR) was used for anemometrie a : laser a : anemometry a: laser a: anemometric a: a : a : light anemometer b : laser A : laser
Abstract: Keywords: anemometrie a : laser ; anemometrie ; optique ; laser : Doppler Reference Record created on 2005-11-18, modified on 2016-08-08
850 citations
TL;DR: In this article, a tunable high-power free-electron laser with a relativistic electron beam in a constant spatially periodic transverse magnetic field has been demonstrated, achieving a gain of 7% per pass at an electron current of 70 mA.
Abstract: Gain has been observed for optical radiation at 10.6 \ensuremath{\mu}m due to stimulated radiation by a relativistic electron beam in a constant spatially periodic transverse magnetic field. A gain of 7% per pass was obtained at an electron current of 70 mA. The experiments indicate the possibility of a new class of tunable high-power free-electron lasers.
496 citations
Patent•
Alza1
TL;DR: In this article, a high speed process and apparatus are disclosed for forming outlet passageways of accurate, predetermined size in the walls of pills which dispense their contents by osmotically pumping said contents out of said outlets.
Abstract: A high speed process and apparatus are disclosed for forming outlet passageways of accurate, predetermined size in the walls of pills which dispense their contents by osmotically pumping said contents out said outlet passageways. The pills are moved in succession by an indexer past a passageway forming station where the pills are tracked seriatim at the velocity at which they are moving by an optical tracking system focused on the pill wall and into which a laser beam is directed. During the tracking the laser is fired and the laser beam is transmitted by the optical tracking system onto the wall of the moving pill, the laser power, laser beam dimensions and firing duration being such as to cause the laser beam to heat and pierce the pill wall, thereby forming said outlet passageway.
428 citations
TL;DR: In this article, the authors used the Judd-Ofelt (J-O) theory for crystal-field-induced electric-dipole transitions and demonstrated that Nd-doped glasses can be tailored for specific laser applications by proper selection of the glass constituents.
Abstract: Systematic studies of spectral intensities using the Judd-Ofelt (J-O) theory for crystal-field-induced electric-dipole transitions demonstrate that Nd-doped glasses can be tailored for specific laser applications by proper selection of the glass constituents. Variations with glass composition are reported for the following properties: induced-emission cross section, peak fluorescence wavelength, effective fluorescence bandwidth, radiative lifetime, transition probabilities, and fluorescence branching ratios. Both glass network formers and network-modifier ions were changed. In these studies the induced-emission cross section for the Nd3+,4 F_{3/2} \rightarrow 4 I_{11/2} laser transition was varied by more than a factor of 4 by changing the glass host.
314 citations
TL;DR: In this paper, the method of conformal transformations is applied to the analysis of waveguide bends and simple first-order expressions that describe the dependence of the losses on waveguide parameters are derived.
Abstract: The method of conformal transformations is applied to the analysis of waveguide bends. Equivalent structures are obtained that permit solution by traditional methods of optical waveguide analysis. Losses associated with both curvature and with the transition from straight to curved guides are discussed and simple first-order expressions that describe the dependence of the losses on waveguide parameters are derived.
299 citations
TL;DR: In this article, a ranging system, consisting of a laser, computer-controlled optical deflection assembly, and TV camera, obtains three-dimensional images of curved solid objects, which are then segmented into parts by grouping parallel traces obtained from the ranging system.
Abstract: A ranging system, consisting of a laser, computer-controlled optical deflection assembly, and TV camera, obtains three-dimensional images of curved solid objects. The object is segmented into parts by grouping parallel traces obtained from the ranging system. Making use of the property of generalized translational invariance, the parts are described in terms of generalized cylinders, consisting of a space curve, or axis, and a circular cross section function on this axis.
284 citations
TL;DR: In this article, the authors considered CW passive mode locking of a homogeneously broadened laser and showed that it is possible to achieve single-pulse mode locking by a saturable absorber.
Abstract: CW passive mode locking of a homogeneously broadened laser is considered. In the coordinate plane, whose abscissa is proportional to the small-signal saturable absorber loading, and whose ordinate is proportional to the small-signal gain, the following regimes are laid out: 1) steady-state single-pulse mode-locking solutions; 2) stability against relaxation oscillations; 3) self-starting of mode locking. The assumption is made that CW mode locking can be obtained only for a choice of parameters for which all three regimes overlap. We require further that the overlap regime be reached by a monotonic increase of small-signal gain (pumping), without passing outside regime 2). Under these conditions one may state requirements on the system parameters for the obtainment of single-pulse mode locking by a saturable absorber. The analysis explains why it has been impossible to mode lock passively the CW Nd:YAG laser, but passive mode locking of the CW dye-laser system is possible.
225 citations
TL;DR: In this paper, drift compensation and scan calibration of a visible-to-infrared difference-frequency converter enabling high-resolution molecular spectra to be recorded with a precision and reproducibility of 5 × 10−4 cm−1.
Abstract: Techniques are described for drift compensation and scan calibration of a visible-to-infrared difference-frequency converter enabling high-resolution molecular spectra to be recorded with a precision and reproducibility of 5 × 10−4 cm−1. The capabilities of the spectrometer are illustrated by scans of the tetrahedral fine structure in the ν3 band of methane under low pressure, Doppler-limited and atmospheric pressure, collision-broadened conditions.
TL;DR: In this paper, an automatic fringe counting interferometer with real-time wavelength readout for cw laser sources is described, and absolute wavelength accuracy is demonstrated with saturated absorption spectroscopy in neon.
Abstract: We describe an automatic fringe‐counting interferometer with real‐time wavelength readout for cw laser sources. Sub‐Doppler absolute wavelength accuracy (∼2×10−7) is demonstrated with saturated absorption spectroscopy in neon.
TL;DR: In this article, single pulses from a well-calibrated mode-locked YAlG:Nd laser have been used to measure the two-photon absorption coefficient at 1.064 µm in several semiconductors.
Abstract: Single pulses from a well-calibrated mode-locked YAlG:Nd laser have been used to measure the two-photon absorption coefficient at 1.064 \ensuremath{\mu}m in several semiconductors. The materials studied are four direct-gap semiconductors, GaAs, CdTe, ZnTe, and CdSe, and one indirect-gap semiconductor, GaP. The results for the direct-gap semiconductors are interpreted with respect to the imaginary part of the third-order nonlinear susceptibility ${\ensuremath{\chi}}_{1111}^{(3)}(\ensuremath{-}\ensuremath{\omega},\ensuremath{\omega},\ensuremath{\omega},\ensuremath{-}\ensuremath{\omega})$. An anisotropy of the two-photon absorption coefficient is observed in GaAs.
TL;DR: In this article, the first observation of ionization of dense Na vapor by laser radiation was reported, where a 1MW pulsed laser at 589.6 nm was used to ionize a 10-Torr-cm column of Na.
Abstract: We report the first observation of ionization of dense Na vapor by laser radiation. A 1-MW pulsed laser at 589.6 nm produced almost complete ionization of a 10-Torr-cm column of Na. Measurements of the Na/sup +/ photoionizaton cross section, the neonlike series 2s/sup 2/p/sup 6/..-->..2s/sup 2/2p/sup 5/ns and nd, and several autoionizing resonances of the type 2s/sup 2/2p/sub 6//sup 6/..-->..2s2p/sup 6/np were obtained using a spark source to provide the continuum background for absorption spectroscopy of the ion. (AIP)
01 Jan 1976
TL;DR: Atomic and molecular spectroscopy with lasers has been studied in this paper, including double-resonance spectrograms of molecules by means of laser-Raman spectroscopes.
Abstract: Atomic and molecular spectroscopy with lasers.- Infrared spectroscopy with tunable lasers.- Double-resonance spectroscopy of molecules by means of lasers.- Laser Raman spectroscopy of gases.- Linear and nonlinear phenomena in laser optical pumping.- Laser frequency measurements, the speed of light, and the meter.
TL;DR: In this paper, it was shown that a single dye-laser pulse can induce a Kerr effect at Raman-shifted frequencies. But this effect was shown to induce a small fraction of the power required to produce stimulated instabilities.
Abstract: A new effect is demonstrated in which a laser pulse can be made to induce a Kerr effect only at Raman-shifted frequencies. This permitted the observation of a Raman spectrum with a single dye-laser pulse. The pulse power required is a small fraction of that required to produce stimulated instabilities. The spectral information emerges in a coherent beam, phase matching is not necessary, and spectra can be obtained at any scattering angle.
Book•
01 Jan 1976
TL;DR: The available literature and research work in chemical lasers which was published and performed between 1967 and 1974 are collected and critically reviewed as discussed by the authors, and a detailed review of the CO chemical laser and a comprehensive collection of the work in high power iodine laser are given.
Abstract: The available literature and research work in chemical lasers which was published and performed between 1967 and 1974 are collected and critically reviewed. Basic reviews are presented on the chemical kinetics of nonequilibrium reactions, gas dynamics of reactive flows, and laser physics of high-gain media. The ability to control the kinetics and thermodynamics of highly exothermic reactions by fast supersonic flows is explored. The work done on pulsed chemical lasers, transfer lasers, and numerical modeling of chemical lasers is reviewed. The theory of reactive collision mechanisms leading to the nonequilibrium vibrational excitation of the molecules that constitute the active medium of chemical lasers is covered. A detailed review of the CO chemical laser and a comprehensive collection of the work in high power iodine laser are given. In conclusion, the work performed on metal-atom oxidation lasers at Los Alamos is described. (MHR)
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TL;DR: In this article, an optical fiber ring resonator was used for the observation of efficient continuous-wave Brillouin laser action in an optical-fiber ring resonance, achieving internal laser conversion efficiencies of 50% and a Brillour-shifted output of 20 mW.
Abstract: The observation of efficient continuous‐wave Brillouin laser action in an optical‐fiber ring resonator is reported. Internal laser conversion efficiencies of 50% and a Brillouin‐shifted output of 20 mW have been achieved.
TL;DR: In this article, the fundamental physical principles essential to an understanding of waveguide gas and liquid lasers, and the current technological state of these devices are discussed, as well as their applications and their current state of the art.
Abstract: The present article reviews the fundamental physical principles essential to an understanding of waveguide gas and liquid lasers, and the current technological state of these devices. At the present time, waveguide laser transitions span the visible through submillimeter regions of the wavelength spectrum. The introduction discusses the many applications of waveguide lasers and the wide variety of laser configurations that are possible. Section 1 summarizes the properties of modes in hollow dielectric waveguides of circular, rectangular, and planar cross section. Section 2 considers various approaches to optical feedback including internal and external mirror Fabry-Perot type resonators, hollow waveguide distributed feedback structures, and ring-resonant configurations. Section 3 discusses those aspects of molecular kinetic and laser theory pertinent to the design and optimization of waveguide gas lasers such as the scaling laws for discharge-excited gas lasers, molecular models useful in maximizing the oscillation bandwidth, the effects of gas flow rate, and the physics of optically-pumped far-infrared lasers. Finally, a review of the waveguide gas and liquid lasers reported to date is given in Section 4.
PARC1
TL;DR: In this paper, a general formulation for arbitrary-shaped gratings which need not be small in size was developed for radiated power from traveling waves as a function of grating tooth height, tooth width, refractive index, waveguide thickness, and period.
Abstract: Grating-coupled radiation in GaAs:GaAlAs lasers and waveguides is analyzed. A general formulation is developed for arbitrary-shaped gratings which need not be small in size. Two methods are used to solve the resulting equations in the case of rectangular-shaped gratings. The first is a perturbation technique and the second is iterative in nature. The iterative procedure converges to a numerical exact solution in many cases of practical interest and indicates that the perturbation results are quite accurate. Curves are presented for radiated power from traveling waves as a function of grating tooth height, tooth width, refractive index, waveguide thickness, and period for rectangular gratings in heterostructure waveguiding geometries. It is shown that radiation is not a monotonically increasing function of tooth height, but rather maxima occur when the teeth are half the optical wavelength in the material. Also, in particular geometries with an air:GaAs grating interface, radiated power of a mode can exceed 100 cm-1.
TL;DR: In this article, absolute rate constants for the deactivation of O(1D) atoms by some atmospheric gases have been determined by observing the time-resolved emission of ozone at 630 nm.
Abstract: Absolute rate constants for the deactivation of O(1D) atoms by some atmospheric gases have been determined by observing the time-resolved emission of O(1D) at 630 nm. O(1D) atoms were produced by the dissociation of ozone via repetitive laser pulses at 266 nm. Absolute rate constants for the relaxation of O(1D) at 298 K are reported for N2, O2, CO2, O3, H2, D2, CH4, HCl, NH3, H2O, N2O, and Ne. The results obtained are compared with previous relative and absolute measurements reported in the literature.
TL;DR: In this article, a new technique for use in coherent anti-Stokes Raman scattering experiments allows the simultaneous generation of an entire Q-branch spectrum of the anti-stokes radiation from a molecular gas using a single laser pulse.
Abstract: A new technique for use in coherent anti‐Stokes Raman scattering experiments allows the simultaneous generation of an entire Q‐branch spectrum of the anti‐Stokes radiation from a molecular gas using a single laser pulse. With this technique the stringent requirements of the previous techniques concerning laser linewidth and frequency stability are significantly relaxed. The excellent temporal resolution (20 nsec) makes the technique very attractive for temperature and concentration measurements of molecular gases, even in nonstationary media.
TL;DR: In this article, XeF, KrF, and ArF have been excited in a uv−preionized transverse electric discharge with peak powers of several megawatts.
Abstract: Lasers in XeF, KrF, and ArF have been excited in a uv‐preionized transverse electric discharge. Laser pulse energies exceeding 100 mJ with peak powers of several megawatts have been produced with electrical efficiencies of over 1%.
TL;DR: In this article, the authors present a completely classical analysis of the small-signal regime of a free-electron laser and show that the amplification is due to stimulated scattering produced by a bunching of the electron distribution.
TL;DR: This article proposed powder metallurgy, which allows the homogeneous melt to be cooled in tiny droplets, making it possible at least to limit segregation to the scale of the resulting powder particles.
Abstract: How can we make an alloy to fit a specific materials requirement? The oldest method of alloy fabrication, casting, has two inherent limitations: Phases with high melting points are difficult to melt; and the cooling of the alloys from the melt is slow, so that alloy segregation and phase separation have time to occur. The other traditional method, powder metallurgy, has helped with the second of these problems: Allowing the homogeneous melt to be cooled in tiny droplets makes it possible at least to limit segregation to the scale of the resulting powder particles.
TL;DR: In this article, a theory of the nitrogen laser is presented which treats the laser as an integrated electrooptical system based upon the known macroscopic properties of nitrogen discharges along with the known electron impact ionization and excitation cross sections for the N 2 molecule.
Abstract: We have studied several types of flat-plate-transmission-line pulse-excited nitrogen lasers. Experiments were carried over a wide variety of parameters such as laser-tube pressure, charging voltage, laser-tube inductance, transmission-line impedance, and others. A theory of the nitrogen laser is presented which treats the laser as an integrated electrooptical system. The theory is based upon the known macroscopic properties of nitrogen discharges along with the known electron impact ionization and excitation cross sections for the N 2 molecule. The theoretical predictions are in very good agreement with the experimental observations. It is suggested that this type of theoretical approach should be applicable to fast high-power discharges in many other gases.
TL;DR: In this paper, the formation and decay rate constants of the DODCI photoisomer were found to follow an Arrhenius law with respectively an activation energy of 4.5 ± 0.4 kcal/M and 14.3 kcal/m.
TL;DR: In this article, simplified models are used to show how the various atmospheric effects interrelate and impact on the best laser choice for high power applications through their dependence on the laser wavelength and temporal mode (e.g., cw or pulsed) of operation.
Abstract: High power laser beams propagating in the atmosphere are subjected to a variety of effects, the most important of which are absorption, scattering, turbulence induced beam spreading and wander, thermal blooming, and gas breakdown. In this paper simplified models are used to show how the various atmospheric effects interrelate and impact on the best laser choice for high power applications through their dependence on the laser wavelength and temporal mode (e.g., cw or pulsed) of operation. Results for sea level propagation at seven common laser wavelengths varying from 0.34 microm to 10.6 microm. are presented that show the mid-ir wavelengths to be favored for typical turbulence and aerosol scattering conditions. At the longer 10.6-microm CO(2) laser wavelength thermal blooming is dominant due to stronger molecular absorption, while at the shorter wavelengths turbulence induced beam spreading and aerosol absorption and scattering effects become important and tend to limit the increase in irradiance expected on the basis of diffraction effects alone.
TL;DR: In this paper, a Rhodamine 6G dye laser with a thin optically contacted saturable absorber cell has been mode locked over an operating frequency range of 598-615 nm to produce pulses with durations as short as 0.3 ps.
Abstract: A cw Rhodamine 6G dye laser with a thin optically contacted saturable absorber cell has been mode locked over an operating frequency range of 598–615 nm to produce pulses with durations as short as 0.3 ps. The pulses, with sech2 intensity profiles, are practically bandwidth limited.